An adjustable rate mortgage, or ARM as it is popularly known as, is a mortgage loan [1] in which the interest rate on the note [2] is periodically adjusted based on a variety of indices [3]. Different lenders use different indices to calculate their interest rates, or their adjustable rates. Some of the commonly used indices are the 1-year constant-maturity Treasury (CMT) securities, the Cost of Funds Index (COFI), and the London Interbank Offered Rate (LIBOR). However, a few lenders prefer to use their personal or own indices to determine the rates. Lenders may choose to do this to avail a steady margin from the borrower, and their own cost of funding is related to the index. As a result, the payments made by the borrower may also change over time in accordance to the fluctuations in the resultant interest rates. Typically, the adjustable rate mortgages are characterized by their index and their limitations on charges or caps [4]. In many countries, the adjustable rate mortgages are the standard means of availing finance by offering the homes as securities, and in such cases, the credit facility is simply referred to as a mortgage.

Basic features of ARM or adjustable mortgage

The main features of ARM are:

1. The initial interest rate It is the rate of interest associated with the ARM at the time of conception of the loan facility. The initial ARM rate is generally well below the existing current ARM market rates charged during subsequent years.
2. The adjustment period This is the actual length of time, of the total loan period of the ARM, which is scheduled to remain constant or unchanged. The interest rate is reset at the end of the adjustment period, and the monthly loan repayment options are recalculated.
3. Index rate Majority of the lenders prefer to associate the ARM mortgage interest rates changes with changes occurring in a particular index. As stated previously, lenders generally set the ARM rates on a variety of indices. The most common index rate used is one, three, or five years treasury securities index. Another commonly used index is the national or regional average cost of funds to savings and loan associations index.
4. The profit margin The profit is calculated by adding a certain percentage of the loan amount to the amount of the base index rate. The difference of the net payable loan amount minus the base index amount is the actual profit enjoyed by the lender in an ARM.
5. Adjustments and interest rates ARMs provide a unique adjustment period for borrowers during the inception of the loan facilities. The rate structure can change at the end of the adjustment period. However, several lenders provide more than one adjustment periods. It is possible for the borrowers to change certain aspects of the net payable interest rates with each new adjustment period. So there is an advantage to avail different interest rates with individual adjustment periods. If the borrower is market savvy, he or she can select different indices or interest rates and save money, provided the lender agrees to the rates and indices.
6. Initial discounts Initial discounts are interest rate concessions, and are very commonly used as promotional aids to attract customers for ARMs. Such discounts are only offered during the first year of the ARM loan. The discounts help to reduce the interest rate below the prevailing rate for a certain duration of time so the borrower can save some money through temporary reduced rates.
7. Negative amortization[5] Ideally, the net chargeable interest rate decreases with a regular payment of monthly dues against any credit borrowings. In case of mortgages the rates decrease over a period as loan pay offs occur. However, in case of ARMs, the reverse happens, and the mortgage balance actually increases whenever the ARM base index rates climb up. As the ARM base index increases in magnitude, its associated interest amount and repayment cap also increases, and the borrower ends up paying a greater amount to redeem the loan. This is a negative feature of ARMs and the borrower may suffer a certain loss over the loan tenure until redemption occurs.
8. Conversion to a different loan format ARMs have an agreement according to which the borrower can convert the ARM to a fixed-rate mortgage at designated times. This is often a fall back facility in case the ARM does not work in the borrowers favor and the buyer wants to revert to a safe option of a steady rate of interest.
9. Loan prepayment In majority of loans and credit facilities, lenders prefer the borrower redeem their dues as soon as possible, to recover the original lending amount. However, in case of ARMs a prepayment can result into a potential loss for the lender in the long run. So lenders generally include a clause in the ARM agreement which may force the buyer to pay special fees or penalties in case the borrower decides to pay off early. ARM prepayment terms are usually negotiated in the beginning before the credit facility is availed.

Summary

Even though ARMs have a low starting interest rate, there is no indication that the future cost of borrowings will be maintained at the same rate, since the base index rate is likely to change. If the indices rise, the net ARM cost will also be higher, and the borrower will have to pay a higher loan amount. So there is an inherent risk involved with ARMs. Certain studies indicate that on average, the majority of borrowers opting for adjustable rate mortgages save money in the long term.

Legend

[1] A mortgage loan is a specific type of loan, which is secured by some property or a fixed asset value having a certain financial value through a lien, or a legal written commitment empowering the creditor to sell the security offered in order to recover the outstanding dues, in case the creditor is unable to pay or redeem the borrowed amount. The word mortgage when used alone, in day-to-day life, is often used to convey a mortgage loan.

[2] A written promise to repay or redeem a specified borrowed sum of money, along with its interest at a predefined rate and length of time.

[3] An index rate is a widely used rate of interest generally used by lenders to set the interest rate on loans and credit cards.

[4] Loan capital or amount.

[5] Amortization is a gradual reduction in the value of an asset or liability by some predetermined process. In case of loans, it means a gradual or specific decrease in the magnitude of the net payable interest amount over a period, until the entire loan amount becomes void and is deemed as paid.